1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, more particularly to a photosensitive member which has a photosensitive layer containing an azo pigment having a specific molecular structure.
2. Related Background Art
Organic photoconductive members can be synthesized more easily than inorganic photoconductive members, and yet concerning visible light sensitivity, the sensitive wavelength region can be varied relatively easily by molecular design.
Accordingly, color sensitivity can be controlled, and also from the points such as no pollution as well as productivity and economy which are by far superior to inorganic semiconductors, various competitive companies are developing hastily organic photoconductive members. Many have reached practical levels such as sensitivity, durability, etc., but further improved levels are demanded.
On the other hand, in recent years, there is also arisen rapidly an increasing demand to extend the light-sensitive wavelength region of these organic photosensitive members to the near-infrared wavelength of semiconductor laser (under the present situation, practically most preferably 750 nm or longer, particularly around 780-800 nm, in respect of economy, output, matching with sensitive material, etc.) and use them as the photosensitive member for digital recording such as laser printer, etc. Looking back on the organic photosensitive members of the prior art from this standpoint, there have been proposed phthalocyanine pigments, aluminum phthalocyanine pigments as improvement of phthalocyanine pigments disclosed in U.S. Pat. No. 4,426,434, triphenylamine type trisazo pigments disclosed in U.S. Pat. Nos. 4,436,880 and 4,439,506, tetrakisazo pigments disclosed in U.S. Pat. No. 4,447,513, N-phenyl substituted type diphenylamine type disazopigments, diphenylamine type disazopigments disclosed in Japanese Laid-open Patent Publications Nos. 80643/1983 and 43662/1986, disazo pigments with two coupler portions different from each other and at least one coupler portion having CF.sub.3 group, etc. as the photoconductive member for semiconductor laser.
However, when an organic photoconductive member is used as the photosensitive member for semiconductor laser, it is required that, first, the photosensitive wavelength region should be extended to longer wavelength region; next, sensitivity and durability should be good; since the wavelength of semiconductor laser varies depending on the temperature during use, sensitivity should be constant in the varying region. None of the above organic photoconductive members satisfy sufficiently these various conditions.